Methods are known for preparing compound (I) by selective mono-etherification of pyrocatechin (II) with methallyl halides (III) in the presence of inorganic bases and in aprotic solvents such as dimethylsulphoxide (DMSO) and N-methyl-2-pyrrolidone.
However, the aprotic solvents are expensive and of such relatively low stability that recovery thereof requires particular care and high operating efficiency, which adversely affects both the operation and cost.
On the other hand, the recovery of unreacted pyrocatechin from the resulting reaction mixtures presents some difficulties which entail high losses of pyrocatechin along with a high cost of the operation itself and render it desirable to aim at the highest possible conversion obtainable by employing the aforesaid sophisticated, special solvents.
Nevertheless, operating under conditions directed to attaining very high conversion values involves, in some cases, a practically unavoidable formation of by-products, such as di-methallyl-ether of pyrocatechin of formula (V): ##STR5## as well as of alkylation products on the aromatic ring. In these conditions it is therefore absolutely necessary to reduce as much as possible the formation of such by-products in order to prevent the economic and operating advantages expected from the high conversions from being partially jeopardized.